Systemic infections and inflammation affect chronic neurodegeneration

Inflammation after trauma: microglial activation and traumatic brain injury

OBJECTIVE

Patient outcome after traumatic brain injury (TBI) is highly variable. The underlying pathophysiology of this is poorly understood, but inflammation is potentially an important factor. Microglia orchestrate many aspects of this response. Their activation can be studied in vivo using the positron emission tomography (PET) ligand [11C](R)PK11195 (PK). In this study, we investigate whether an inflammatory response to TBI persists, and whether this response relates to structural brain abnormalities and cognitive function.

METHODS

Ten patients, studied at least 11 months after moderate to severe TBI, underwent PK PET and structural magnetic resonance imaging (including diffusion tensor imaging). PK binding potentials were calculated in and around the site of focal brain damage, and in selected distant and subcortical brain regions. Standardized neuropsychological tests were administered.

RESULTS

PK binding was significantly raised in the thalami, putamen, occipital cortices, and posterior limb of the internal capsules after TBI. There was no increase in PK binding at the original site of focal brain injury. High PK binding in the thalamus was associated with more severe cognitive impairment, although binding was not correlated with either the time since the injury or the extent of structural brain damage.

INTERPRETATION

We demonstrate that increased microglial activation can be present up to 17 years after TBI. This suggests that TBI triggers a chronic inflammatory response particularly in subcortical regions. This highlights the importance of considering the response to TBI as evolving over time and suggests interventions may be beneficial for longer intervals after trauma than previously assumed.

Repertoire of microglial and macrophage responses after spinal cord injury

Macrophages from the peripheral circulation and those derived from resident microglia are among the main effector cells of the inflammatory response that follows spinal cord trauma. There has been considerable debate in the field as to whether the inflammatory response is good or bad for tissue protection and repair. Recent studies on macrophage polarization in non-neural tissues have shed much light on their changing functional states. In the context of this literature, we discuss the activation of macrophages and microglia following spinal cord injury, and their effects on repair. Harnessing their anti-inflammatory properties could pave the way for new therapeutic strategies for spinal cord trauma.

Exacerbation of CNS inflammation and neurodegeneration by systemic LPS treatment is independent of circulating IL-1β and IL-6

Background

Chronic neurodegeneration comprises an inflammatory response but its contribution to the progression of disease remains unclear. We have previously shown that microglial cells are primed by chronic neurodegeneration, induced by the ME7 strain of prion disease, to synthesize limited pro-inflammatory cytokines but to produce exaggerated responses to subsequent systemic inflammatory insults. The consequences of this primed response include exaggerated hypothermic and sickness behavioural responses, acute neuronal death and accelerated progression of disease. Here we investigated whether inhibition of systemic cytokine synthesis using the anti-inflammatory steroid dexamethasone-21-phosphate was sufficient to block any or all of these responses.

Methods

ME7 animals, at 18-19 weeks post-inoculation, were challenged with LPS (500 μg/kg) in the presence or absence of dexamethasone-21-phosphate (2 mg/kg) and effects on core-body temperature and systemic and CNS cytokine production and apoptosis were examined.

Results

LPS induced hypothermia and decreased exploratory activity. Dexamethasone-21-phosphate prevented this hypothermia, markedly suppressed systemic IL-1β and IL-6 secretion but did not prevent decreased exploration. Furthermore, robust transcription of cytokine mRNA occurred in the hippocampus of both ME7 and NBH (normal brain homogenate) control animals despite the effective blocking of systemic cytokine synthesis. Microglia primed by neurodegeneration were not blocked from the robust synthesis of IL-1β protein and endothelial COX-2 was also robustly synthesized. We injected biotinylated LPS at 100 μg/kg and even at this lower dose this could be detected in blood plasma. Apoptosis was acutely induced by LPS, despite the inhibition of the systemic cytokine response.

Conclusions

These data suggest that LPS can directly activate the brain endothelium even at relatively low doses, obviating the need for systemic cytokine stimulation to transduce systemic inflammatory signals into the brain or to exacerbate existing pathology.

Accumulation of murine subretinal macrophages: effects of age, pigmentation and CX3CR1

Macrophages or activated microglia in the subretinal space are considered a hallmark of some retinal pathologies. We investigated the effects of age, pigmentation and CX(3)CR1 deficiency on the accumulation of macrophages/activated microglia in the outer retina of young and old Cx(3)cr1(gfp/gfp) (CX(3)CR1-deficient) or Cx(3)cr1(gfp/+) mice on either a pigmented (C57BL/6) or albino (BALB/c) background. Quantitative analysis of immunostained retinal-choroidal whole mounts revealed an increase in subretinal macrophage (SRMΦ) numbers in young Cx(3)cr1(gfp/gfp) mice compared with Cx(3)cr1(gfp/+) mice, however the increase was more marked in albino Cx(3)cr1(gfp/gfp) mice. In aged mice, large numbers of SRMΦ/activated microglia replete with autofluorescent debris were noted in both old pigmented Cx(3)cr1(gfp/gfp) and Cx(3)cr1(gfp/+) mice proving this accumulation was not CX(3)CR1-dependent. While CX(3)CR1 deficiency leads to an early onset of SRMΦ accumulation, our data reveal that this change occurs in both aged Cx(3)cr1(gfp/+) and Cx(3)cr1(gfp/gfp) pigmented mice in the absence of marked retinal degeneration and is likely a normal response to aging.

Adenosine A(2A) Receptor and IL-10 in Peripheral Blood Mononuclear Cells of Patients with Mild Cognitive Impairment

Adenosine suppresses immune responses through the A_2A receptor (A_2AR). This study investigated the interleukin 10 (IL-10) genetic profile and the expression of A_2AR in peripheral blood mononuclear cells (PBMCs) of patients with mild cognitive impairment (MCI), Alzheimer disease (AD), and age-matched controls to verify, if they may help distinguish different forms of cognitive decline. We analyzed the IL-10 genotype and the expression of A_2AR in 41 subjects with AD, 10 with amnestic MCI (a-MCI), 49 with multiple cognitive domain MCI (mcd-MCI), and 46 controls. There was a significant linear increase in A_2AR mRNA levels and A_2AR density from mcd-MCI to a-MCI, with intermediate levels being found in AD. The IL-10 AA genotype frequency was 67% in a-MCI, 46% in AD, 35% in mcd-MCI, and 20% in controls. These data suggest that the assessment of the IL-10 genotype and the expression of A_2AR in PBMCs may be a valuable means of differentiating between a-MCI and mcd-MCI.

DNA methylation in neurodegenerative disorders: a missing link between genome and environment?

The risk of developing neurodegenerative disorders such as Alzheimer's disease or Parkinson's disease is influenced by genetic and environmental factors. Environmental events occurring during development or later in life can be related to disease susceptibility. One way by which the environment may exert its effect is through epigenetic modifications, which might affect the functioning of genes. These include nucleosome positioning, post-translational histone modifications, and DNA methylation. In this review we will focus in the potential role of DNA methylation in neurodegenerative disorders and in the approaches to explore such epigenetic changes. Advances in deciphering the role of epigenetic modifications in phenotype are being uncovered for a variety of diseases, including cancer, autoimmune, neurodevelopmental and cognitive disorders. Epigenetic modifications are now being also associated with cardiovascular and metabolic traits, and they are expected to be especially involved in learning and memory processes, as well as in neurodegenerative disease. The study of the role of methylation and other epigenetic modifications in disease development will provide new insights in the etiopathogenesis of neurodegenerative disorders, and should hopefully shape new avenues in the development of therapeutic strategies.

Mechanisms of Resolution of Inflammation

The inflammatory response is an integral part of the innate immune mechanism that is triggered in response to a real or perceived threat to tissue homeostasis, with a primary aim of neutralizing infectious agents and initiating repair to damaged tissue. By design, inflammation is a finite process that resolves as soon as the threat of infection abates and sufficient repair to the tissue is complete. Resolution of inflammation involves apoptosis and subsequent clearance of activated inflammatory cells – a tightly regulated event. Chronic inflammation is a characteristic feature in virtually all inflammatory diseases, including atherosclerosis, and it is becoming increasingly clear that derangement of the processes usually involved in resolution of inflammation is an underlying feature of chronic inflammatory conditions. This review will draw on evidence from a range of diseases in which dysregulated inflammation is important, with particular emphasis on cardiovascular disease.

Non-resolving aspects of acute inflammation after spinal cord injury (SCI): indices and resolution plateau

Inflammatory resolution is an active, highly regulated process already encoded at the onset of inflammation and required to prevent the transition into chronic inflammation associated with spreading of tissue injury and exacerbated scarring. We introduce objective, quantitative measurements [resolution indices (R(i) ) and resolution plateau (R(P) )] to characterize inflammatory resolution and to determine the persistence ("dwell time") of differential leukocyte subpopulations at the lesion site after acute experimental spinal cord injury (SCI). The cell type-specific resolution interval R(i) (time between maximum cell numbers and the point when they are reduced to 50%) ranges from 1.2 days for neutrophils, 1.5 days for T lymphocytes, to 55 days for microglia/macrophages. As the resolution interval neglects exiting cell trafficking in the later period of resolution (49%-0% of lesional cells), we introduced the R(P) , a marker for the persisting, chronified leukocyte subsets, which are likely to participate in late degeneration and non-resolving inflammation. Here, we identify the acute inflammatory response in central nervous system (CNS) lesions as partly non self-limiting. Both extended resolution intervals (reduced leukocyte clearance) and elevated plateaus (permanent lesional cell numbers) provide quantitative measures to characterize residual, sustained inflammation and define cognate timeframes of impaired resolution after acute SCI.

Increased plasma levels of lipocalin 2 in mild cognitive impairment

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by an irreversible cognitive decline and neuronal loss associated with neurofibrillary tangles and senile plaques. Mild cognitive impairment (MCI) is a prodromal stage of AD and is associated with memory loss and a high risk of developing AD. Lipocalin 2 (LCN2) is an acute phase protein. Our previous studies have shown that exposure to inflammatory stimuli resulted in elevated LCN2 levels in brain microglia and astrocytes implicating LCN2 in brain inflammation. Therefore, we hypothesize that there may be a significant change in the plasma LCN2 levels in patients with MCI and AD when compared to healthy control subjects.

METHODS

Forty-one patients with MCI, 62 patients with AD and 38 healthy elderly control subjects were recruited for this study. They were given a comprehensive battery of neuropsychological tests including a mini-mental status examination (MMSE) and clinical dementia rating (CDR). A variety of clinical information was collected from the semi-structured questionnaire administered. The LCN2 levels were measured using a specific enzyme-linked immunosorbent assay in the plasma, which had been collected early in the morning after overnight fasting.

RESULTS

The LCN2 levels were significantly higher in MCI patients compared to the healthy control subjects and AD patients [control vs. MCI (p=0.005); MCI vs. AD (p=0.009)]. There was a significant negative correlation between the LCN2 levels and CDR scores (r=-0.245, p=0.014), and there was a positive correlation between the LCN2 levels and MMSE scores (r=0.317, p=0.001) among all of the MCI and AD patients.

CONCLUSION

MCI represents a prodromal stage of AD, and inflammation occurs as one of the earliest pathological events in AD. Thus, increased plasma LCN2 levels during MCI could be helpful in predicting the progression from MCI to AD.

Identification of anti-inflammatory targets for Huntington's disease using a brain slice-based screening assay

Huntington's disease (HD) is a late-onset, neurodegenerative disease for which there are currently no cures nor disease-modifying treatments. Here we report the identification of several potential anti-inflammatory targets for HD using an ex vivo model of HD that involves the acute transfection of human mutant huntingtin-based constructs into rat brain slices. This model recapitulates key components of the human disease, including the formation of intracellular huntingtin protein (HTT)-containing inclusions and the progressive neurodegeneration of striatal neurons-both occurring within the native tissue context of these neurons. Using this "high-throughput biology" screening platform, we conducted a hypothesis-neutral screen of a collection of drug-like compounds which identified several anti-inflammatory targets that provided neuroprotection against HTT fragment-induced neurodegeneration. The nature of these targets provide further support for non-cell autonomous mechanisms mediating significant aspects of neuropathogenesis induced by mutant HTT fragment proteins.

Minozac treatment prevents increased seizure susceptibility in a mouse "two-hit" model of closed skull traumatic brain injury and electroconvulsive shock-induced seizures

The mechanisms linking traumatic brain injury (TBI) to post-traumatic epilepsy (PTE) are not known and no therapy for prevention of PTE is available. We used a mouse closed-skull midline impact model to test the hypotheses that TBI increases susceptibility to seizures in a "two-hit" injury model, and that suppression of cytokine upregulation after the first hit will attenuate the increased susceptibility to the second neurological insult. Adult male CD-1 mice underwent midline closed skull pneumatic impact. At 3 and 6 h after impact or sham procedure, the mice were injected IP with either Minozac (Mzc), a suppressor of proinflammatory cytokine upregulation, or vehicle (saline). On day 7 after sham operation or TBI, seizures were induced using electroconvulsive shock (ECS), and susceptibility to seizures was measured by the current required for seizure induction. Activation of glia, neuronal injury, and metallothionein-immunoreactive cells were quantified in the hippocampus by immunohistochemical methods. Neurobehavioral function over 14-day recovery was quantified using the Barnes maze. Following TBI there was a significant increase in susceptibility to seizures induced by ECS, and this susceptibility was prevented by suppression of cytokine upregulation with Mzc. Astrocyte activation, metallothionein expression, and neurobehavioral impairment were also increased in the two-hit group subjected to combined TBI and ECS. These enhanced responses in the two-hit group were also prevented by suppression of proinflammatory cytokine upregulation with Mzc. These data implicate glial activation in the mechanisms of epileptogenesis after TBI, and identify a potential therapeutic approach to attenuate the delayed neurological sequelae of TBI.

Systemic LPS administration induces brain inflammation but not dopaminergic neuronal death in the substantia nigra

It has been suggested that brain inflammation is important in aggravation of brain damage and/or that inflammation causes neurodegenerative diseases including Parkinson's disease (PD). Recently, systemic inflammation has also emerged as a risk factor for PD. In the present study, we evaluated how systemic inflammation induced by intravenous (iv) lipopolysaccharides (LPS) injection affected brain inflammation and neuronal damage in the rat. Interestingly, almost all brain inflammatory responses, including morphological activation of microglia, neutrophil infiltration, and mRNA/protein expression of inflammatory mediators, appeared within 4-8 h, and subsided within 1-3 days, in the substantia nigra (SN), where dopaminergic neurons are located. More importantly, however, dopaminergic neuronal loss was not detectable for up to 8 d after iv LPS injection. Together, these results indicate that acute induction of systemic inflammation causes brain inflammation, but this is not sufficiently toxic to induce neuronal injury.

Systemic and central immunity in Alzheimer's disease: therapeutic implications

Clinical pharmaceutical trials aimed at modulating the immune system in Alzheimer's Disease have largely focused on either dampening down central proinflammatory innate immunity or have manipulated adaptive immunity to facilitate the removal of centrally deposited beta amyloid. To date, these trials have had mixed clinical therapeutic effects. However, a number of clinical studies have demonstrated disturbances of both systemic and central innate immunity in Alzheimer's Disease and attention has been drawn to the close communication pathways between central and systemic immunity. This paper highlights the need to take into account the potential systemic effects of drugs aimed at modulating central immunity and the possibility of developing novel therapeutic approaches based on the manipulation of systemic immunity and its communication with the central nervous system.

Cerebellar alterations and gait defects as therapeutic outcome measures for enzyme replacement therapy in α-mannosidosis

α-Mannosidosis is a rare lysosomal storage disease with accumulation of undegraded mannosyl-linked oligosaccharides in cells throughout the body, most notably in the CNS. This leads to a broad spectrum of neurological manifestations, including progressive intellectual impairment, disturbed motor functions, and cerebellar atrophy. To develop therapeutic outcome measures for enzyme replacement therapy that could be used for human patients, a gene knockout model of α-mannosidosis in mice was analyzed for CNS pathology and motor deficits. In the cerebellar molecular layer, α-mannosidosis mice display clusters of activated Bergman glia, infiltration of phagocytic macrophages, and accumulation of free cholesterol and gangliosides (GM1), notably in regions lacking Purkinje cells. α-Mannosidosis brain lysates also displayed increased expression of Lamp1 and hyperglycosylation of the cholesterol binding protein NPC2. Detailed assessment of motor function revealed age-dependent gait defects in the mice that resemble the disturbed motor function in human patients. Short-term enzyme replacement therapy partially reversed the observed cerebellar pathology with fewer activated macrophages and astrocytes but unchanged levels of hyperglycosylated NPC2, gangliosides, and cholesterol. The present study demonstrates cerebellar alterations in α-mannosidosis mice that relate to the motor deficits and pathological changes seen in human patients and can be used as therapeutic outcome measures.

Parkinson's disease and systemic inflammation

Peripheral inflammation triggers exacerbation in the central brain's ongoing damage in several neurodegenerative diseases. Systemic inflammatory stimulus induce a general response known as sickness behaviour, indicating that a peripheral stimulus can induce the synthesis of cytokines in the brain. In Parkinson's disease (PD), inflammation was mainly associated with microglia activation that can underlie the neurodegeneration of neurons in the substantia nigra (SN). Peripheral inflammation can transform the “primed” microglia into an “active” state, which can trigger stronger responses dealing with neurodegenerative processes. Numerous evidences show that systemic inflammatory processes exacerbate ongoing neurodegeneration in PD patient and animal models. Anti-inflammatory treatment in PD patients exerts a neuroprotective effect. In the present paper, we analyse the effect of peripheral infections in the etiology and progression in PD patients and animal models, suggesting that these peripheral immune challenges can exacerbate the symptoms in the disease.

Alzheimer's disease: current status of etiopathogenesis and therapeutic strategies

Alzheimer's Disease (AD) is one of the most common age-related neurodegenerative diseases. It is the most prevalent form of dementia, a general term for memory loss. It is characterized by progressive cognitive dysfunction, various behavioral and neuro-psychiatric disturbances that seriously interfere with daily life. Scientists have identified factors that appear to play a role in the development of AD but no definitive causes have been found for this complex disorder. The pathogenesis of Alzheimer's disease is highly complex. While several pathologies characterize this disease, amyloid plaques and neurofibrillary tangles are hallmark neuropathological lesions in AD brain. Current AD therapies are merely palliative and only temporarily slow cognitive decline and treatments that address the underlying pathologic mechanisms of AD are still lacking. In this review, we focus on the current aspects of AD ranging from the key risk factors for AD, the underlying pathogenic events and the novel medications including disease-modifying properties.

Inflammatory mechanisms of neurodegeneration in toxin-based models of Parkinson's disease

Parkinson's disease (PD) has been associated with exposure to a variety of environmental agents, including pesticides, heavy metals, and organic pollutants; and inflammatory processes appear to constitute a common mechanistic link among these insults. Indeed, toxin exposure has been repeatedly demonstrated to induce the release of oxidative and inflammatory factors from immunocompetent microglia, leading to damage and death of midbrain dopamine (DA) neurons. In particular, proinflammatory cytokines such as tumor necrosis factor-α and interferon-γ, which are produced locally within the brain by microglia, have been implicated in the loss of DA neurons in toxin-based models of PD; and mounting evidence suggests a contributory role of the inflammatory enzyme, cyclooxygenase-2. Likewise, immune-activating bacterial and viral agents were reported to have neurodegenerative effects themselves and to augment the deleterious impact of chemical toxins upon DA neurons. The present paper will focus upon the evidence linking microglia and their inflammatory processes to the death of DA neurons following toxin exposure. Particular attention will be devoted to the possibility that environmental toxins can activate microglia, resulting in these cells adopting a “sensitized” state that favors the production of proinflammatory cytokines and damaging oxidative radicals.

Can consuming flavonoids restore old microglia to their youthful state?

Microglial cells, which are resident macrophages in the central nervous system, are "primed" in the aged brain and are hypersensitive to messages emerging from immune-to-brain signaling pathways. Thus, in elderly individuals who have an infection, microglia overreact to signals from the peripheral immune system and produce excessive levels of cytokines, causing behavioral pathology including serious deficits in cognition. Importantly, recent studies indicate dietary flavonoids have anti-inflammatory properties and are capable of mitigating microglial cells in the brains of aged mice. Thus, dietary or supplemental flavonoids and other bioactive agents have the potential to restore the population of microglial cells in the elderly brain to its youthful state. This review briefly describes the immune-to-brain signaling pathways, consequences of microglial cell priming, and the potential of flavonoids to mitigate brain microglia and cognitive deficits induced by inflammatory cytokines.

Postoperative cognitive deficits and neuroinflammation in the hippocampus triggered by surgical trauma are exacerbated in aged rats

Postoperative cognitive dysfunction (POCD) is characterized by the progressive deterioration of intellectual/cognitive function following surgery. It has been suggested that the senile brain, which characteristically expresses higher levels of central proinflammatory cytokines, interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α, is more susceptible to additional insult following surgery. The authors of this study investigated the expression of central cytokines IL-1β, IL-6 and TNF-α and hippocampal glial cell activation in aged and adult rats following partial hepatectomy. Cognitive function was assessed in a reversal-learning version of the Morris water maze (MWM) before and after surgery. Hippocampal pro-inflammatory cytokines IL-1β, IL-6 and TNF-α and glial cell activation markers glial fibrillary acidic protein (GFAP) and S100β were measured at each time point; CD200 and CD200R were also measured to explore potential mechanisms of glial cell activation. Surgical trauma resulted in impairments in distance and latency only on postoperative day 1 (p<0.001, respectively) in adult rats. Aged rats exhibited impairments on day 1 (p<0.001) that persisted until postoperative day 3 (p=0.002 and p=0.001, respectively). All significant impairments paralleled upregulated cytokine IL-1β and IL-6 expression. Immunohistochemistry assay further showed more hippocampal glial cell activation in aged rats compared to that in adults. Overall, these findings suggest that surgical trauma, rather than anesthesia, resulted in cognitive function impairment potentiated by aging. Hippocampal pro-inflammatory cytokines and glial cell activation might mediate trauma-induced POCD.

Dysregulated neuronal-microglial cross-talk during aging, stress and inflammation

Communication between neurons and microglia is essential for maintaining homeostasis in the central nervous system (CNS) during both physiological and inflammatory conditions. While microglial activation is necessary and beneficial in response to injury or disease, excessive or prolonged activation can have deleterious effects on brain function and behavior. To prevent inflammation-associated damage, microglia reactivity is actively modulated by neurons in the healthy brain. Age or stress-induced disruption of normal neuronal-microglial communication could lead to an aberrant central immune response when additional stressors are applied. Recent work suggests that both aging and stress shift the CNS microenvironment to a pro-inflammatory state characterized by increased microglial reactivity and a reduction in anti-inflammatory and immunoregulatory factors. This review will discuss how heightened neuroinflammation associated with aging and stress may be compounded by the concomitant loss of neuronally derived factors that control microglial activation, leaving the brain vulnerable to excessive inflammation and neurobehavioral complications upon subsequent immune challenge.

Why mesial temporal lobe epilepsy with hippocampal sclerosis is progressive: uncontrolled inflammation drives disease progression?

Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is a group of chronic disorders characterized by prominent neuronal loss and gliosis in the hippocampus and amygdala. Newly published data indicate that it may be a progressive disease, but the mechanism underlying the progressive nature remains unknown. Recently, substantial evidence for an inflammatory mechanism in MTLE has been documented. We are therefore presenting a review of literature concerning the effects of uncontrolled inflammation on the disease progression of MTLE-HS. We found that increasing amounts of evidence support the association between uncontrolled inflammation and progression of the disease. Uncontrolled inflammatory processes may be a main mechanism underlying the self-propagating cycle of uncontrolled inflammation, blood-brain barrier damage, and seizures that drive the progressive nature. Thus it is important to unravel the principles of communication between the different factors in this cycle. The dynamic modulation of inflammatory processes aimed at preventing or interrupting this cycle has the potential to emerge as a novel therapeutic strategy. This line of therapy might offer new perspectives on the pharmacologic treatment of seizures, and possibly on delaying disease progression or retarding epileptogenesis as well.

A meta-analysis of cytokines in Alzheimer's disease

BACKGROUND

Studies suggest that inflammation is involved in the neurodegenerative cascade leading to Alzheimer's disease (AD) pathology and symptoms. This study sought to quantitatively summarize the clinical cytokine data.

METHODS

Original English language peer-reviewed studies measuring cytokine concentrations in AD and healthy control subjects were included. Mean (± standard deviation) cytokine concentrations for AD and control subjects were extracted.

RESULTS

Forty studies measuring peripheral blood cytokine concentrations and 14 measuring cerebrospinal fluid (CSF) cytokine concentrations were included. In peripheral blood, there were significantly higher concentrations (weighted mean difference [95% confidence interval]) of interleukin (IL)-6 (2.86 [1.68, 4.04] pg/mL, p < .00001, N[AD/control subjects] = 985/680, 14 studies), tumor necrosis factor (TNF)-α (3.25 [.76, 5.74] pg/mL, p = .01, N = 680/447, 14 studies), IL-1β (.55 [.32, .78] pg/mL, p < .00001, N = 574/370, 10 studies), transforming growth factor (TGF)-β (67.23 [28.62, 105.83] pg/mL, p = .0006, N = 190/158, 5 studies), IL-12 (7.60 [5.58, 9.62] pg/mL, p < .00001, N = 148/106, 5 studies), and IL-18 (15.82 [1.98, 29.66] pg/mL, p = .03, N = 131/94, 4 studies) but not of IL-4, IL-8, IL-10, interferon-γ, or C-reactive protein in AD subjects compared with control subjects. There were significantly higher concentrations of TGF-β (7.81 [2.27, 13.35] pg/mL, p =.006, N = 113/114, 5 studies) but not IL-6, TNF-α, and IL-1β in the CSF of AD subjects compared with control subjects.

CONCLUSIONS

These results strengthen the clinical evidence that AD is accompanied by an inflammatory response, particularly higher peripheral concentrations of IL-6, TNF-α, IL-1β, TGF-β, IL-12 and IL-18 and higher CSF concentrations of TGF-β.

Distribution of bone marrow-derived cells in the vestibular end organs and the endolymphatic sac

CONCLUSION

Bone marrow-derived cells (BMDCs) are constitutively present in the vestibular end organs and in the endolymphatic sac, and may play a role in the maintenance of inner ear homeostasis.

OBJECTIVES

The aim was to examine the distribution and characteristics of BMDCs in the vestibular end organs and in the endolymphatic sac.

METHODS

Bone marrow-chimeric mice were generated by bone marrow transplantation from mice genetically labeled with enhanced green fluorescent protein to C57 Bl/6 mice to visualize BMDCs. Three months after bone marrow transplantation, inner ear specimens were processed for histochemical analyses.

RESULTS

BMDCs were widely distributed in the vestibular end organs and the endolymphatic sac, whereas there were differences in the phenotype and the distribution between the vestibular end organs and the endolymphatic sac. A subpopulation of BMDCs in the vestibular end organs expressed antigen-presenting protein MHC class II. Moreover, the density of BMDCs in the vestibular end organs increased in response to local mechanical stress.

Role of neuroinflammation in hypertension-induced brain amyloid pathology

Hypertension and sporadic Alzheimer's disease (AD) have been associated but clear pathophysiological links have not yet been demonstrated. Hypertension and AD share inflammation as a pathophysiological trait. Thus, we explored if modulating neuroinflammation could influence hypertension-induced β-amyloid (Aβ) deposition. Possible interactions among hypertension, inflammation and Aβ-deposition were studied in hypertensive mice with transverse aortic coarctation (TAC). Given that brain Aβ deposits are detectable as early as 4 weeks after TAC, brain pathology was analyzed in 3-week TAC mice, before Aβ deposition, and at a later time (8-week TAC mice). Microglial activation and interleukin (IL)-1β upregulation were already found in 3-week TAC mice. At a later time, along with evident Aβ deposition, microglia was still activated. Finally, immune system stimulation (LPS) or inhibition (ibuprofen), strategies described to positively or negatively modulate neuroinflammation, differently affected Aβ deposition. We demonstrate that hypertension per se triggers neuroinflammation before Aβ deposition. The finding that only immune system activation, but not its inhibition, strongly reduced amyloid burden suggests that stimulating inflammation in the appropriate time window may represent a promising strategy to limit vascular-triggered AD-pathology.

Spinal glia and chronic pain

Therapeutic management of chronic pain has not been widely successful owing to a lack of understanding of factors that initiate and maintain the chronic pain condition. Efforts to delineate the mechanisms underlying pain long have focused on neuronal elements of pain pathways, and both opiate- and non-opiate-based therapeutics are thought largely to target neurons. Abnormal neuronal activity at the level of spinal cord "pain centers" in the dorsal horn leads to hypersensitivity or a hyperalgesic response subsequent to the initial painful stimulus. Only recently has the experimental literature implicated nonneuronal elements in pain because of the realization that glial-derived signaling molecules can contribute to and modulate pain signaling in the spinal cord. Most notably, glial proinflammatory mediators within the dorsal horn of the spinal cord appear to contribute to self-perpetuating pain. Chronic pain is modeled experimentally through a variety of manipulations of sensory nerves including cutting, crushing, resection, and ligation. The cellular and molecular responses in the spinal cord due to these manipulations often reveal activation of 2 types of glia: microglia and astrocytes. The activation states of both microglia and astrocytes are complex and may be driven by underlying chronic neuropathology and/or a chronically "primed" condition that accounts for their contribution to chronic pain. Recent evidence even suggests that opioid tolerance and withdrawal hyperalgesia may be initiated and maintained via actions of microglia and astroglia. Together, these recent findings suggest that glia will serve as novel therapeutic targets for the treatment of chronic pain. To fully exploit glia as novel therapeutic targets will require a greater understanding of glial biology, as well as the identification of agents able to control the glial reactions involved in chronic pain, without interfering with beneficial glial functions.

Brain injury activates microglia that induce neural stem cell proliferation ex vivo and promote differentiation of neurosphere-derived cells into neurons and oligodendrocytes

Brain damage, such as ischemic stroke, enhances proliferation of neural stem/progenitor cells (NSPCs) in the subventricular zone (SVZ). To date, no reliable in vitro systems, which can be used to unravel the potential mechanisms underlying this lesion-induced effect, have been established. Here, we developed an ex vivo method to investigate how the proliferation of NSPCs changes over time after experimental stroke or excitotoxic striatal lesion in the adult rat brain by studying the effects of microglial cells derived from an injured brain on NSPCs. We isolated NSPCs from the SVZ of brains with lesions and analyzed their growth and differentiation when cultured as neurospheres. We found that NSPCs isolated from the brains 1-2 weeks following injury consistently generated more and larger neurospheres than those harvested from naive brains. We attributed these effects to the presence of microglial cells in NSPC cultures that originated from injured brains. We suggest that the effects are due to released factors because we observed increased proliferation of NSPCs isolated from non-injured brains when they were exposed to conditioned medium from cultures containing microglial cells derived from injured brains. Furthermore, we found that NSPCs derived from injured brains were more likely to differentiate into neurons and oligodendrocytes than astrocytes. Our ex vivo system reliably mimics what is observed in vivo following brain injury. It constitutes a powerful tool that could be used to identify factors that promote NSPC proliferation and differentiation in response to injury-induced activation of microglial cells, by using tools such as proteomics and gene array technology.

Contribution of systemic inflammation to chronic neurodegeneration

Systemic infection or inflammation gives rise to signals that communicate with the brain and leads to changes in metabolism and behaviour collectively known as sickness behaviour. In healthy young individuals, these changes are normally transient with no long-term consequences. The microglia are involved in the immune to brain signalling pathways. In the aged or diseased brain, the microglia have a primed phenotype as a consequence of changes in their local microenvironment. Systemic inflammation impacts on these primed microglia and switches them from a relatively benign to an aggressive phenotype with the enhanced synthesis of pro-inflammatory mediators. Recent evidence suggests that systemic inflammation contributes to the exacerbation of acute symptoms of chronic neurodegenerative disease and may accelerate disease progression. The normal homeostatic role that microglia play in signalling about systemic infections and inflammation becomes maladaptive in the aged and diseased brain and this offers a route to therapeutic intervention. Prompt treatment of systemic inflammation or blockade of signalling pathways from the periphery to the brain may help to slow neurodegeneration and improve the quality of life for individuals suffering from chronic neurodegenerative disease.

TGF-β and LPS modulate ADP-induced migration of microglial cells through P2Y1 and P2Y12 receptor expression

Nucleotides act as early signals for microglial recruitment to sites of CNS injury. As microglial motility and activation can be influenced by several local factors at the site of the lesion, we investigated the effects of interferon-gamma, lipopolysaccharide (LPS) or transforming growth factor-β (TGF-β) addition to mixed glial cell cultures, on microglial migration in response to ADP, P2Y12 and P2Y1 mRNA expression as well as on the expression of an array of genes associated with the process of microglial activation. First, we demonstrated, by pharmacological inhibition and by using small interfering RNAs, that in addition to P2Y12, P2Y1 is involved in ADP-stimulated microglial migration. The ability of specific agonists to induce Ca(2+) mobilization further confirmed the expression of functional P2Y receptors in microglia. Then, we found that migratory capability and expression of both P2Y receptors were abrogated in microglial cells from LPS-stimulated mixed glial cultures, while TGF-β increased ADP-induced migration and the expression of P2Y12 and P2Y1 receptors. Interferon-gamma did not influence receptor expression or microglial migration. Finally, the patterns of gene expression induced in microglia by LPS or TGF-β treatment of mixed glial cultures were clearly distinct. LPS induced a set of classical pro-inflammatory genes, whereas TGF-β increased the expression of genes associated with atypical microglial phenotype, namely arginase-1 and TGF-β genes. These results imply that both P2Y1 and P2Y12 may guide microglia toward the lesion. They also suggest that the modulation of microglial purinergic receptors expression by local factors, through direct and/or astrocyte-mediated actions, may represent a novel mechanism affecting neuroinflammatory response.

Aspirin-triggered lipoxin and resolvin E1 modulate vascular smooth muscle phenotype and correlate with peripheral atherosclerosis

Atherosclerosis is a chronic inflammatory disease of the vessel wall. Recent evidence suggests that chronic vascular inflammation ensues as an imbalance between pro- and anti-inflammatory mediators. Recently identified lipid mediators (eg, lipoxins and resolvins) play active roles in promoting the resolution of inflammation. Alterations in vascular smooth muscle cell (VSMC) phenotype, which manifest as a loss of contractile protein expression and increased proliferation and migration, are prominent mechanistic features of both atherosclerosis and restenosis following various interventions (eg, angioplasty and bypass grafting). We sought to determine whether human atherosclerosis is associated with a "resolution deficit" and whether lipoxins and resolvins influence VSMC phenotype. Here we report that plasma levels of aspirin-triggered lipoxin are significantly lower in patients with symptomatic peripheral artery disease than in healthy volunteers. Both aspirin-triggered lipoxin and resolvin E1 block platelet-derived growth factor-stimulated migration of human saphenous vein SMCs and decrease phosphorylation of the platelet-derived growth factor receptor-β. Importantly, receptors for aspirin-triggered lipoxin and resolvin E1 (ALX and ChemR23, respectively) were identified in human VSMCs. Overall, these results demonstrate that stimulatory lipid mediators confer a protective phenotypic switch in VSMCs and elucidate new functions for these mediators in the regulation of SMC biology. These results also suggest that peripheral artery disease is associated with an inflammation-resolution deficit and highlight a potential therapeutic opportunity for the regulation of vascular injury responses.

Neuroinflammation resulting from covert brain invasion by common viruses - a potential role in local and global neurodegeneration

Neurodegenerative diseases are a horrendous burden for their victims, their families, and society as a whole. For half a century scientists have pursued the hypothesis that these diseases involve a chronic viral infection in the brain. However, efforts to consistently detect a specific virus in brains of patients with such diseases as Alzheimer's or multiple sclerosis have generally failed. Neuropathologists have become increasingly aware that most patients with neurodegenerative diseases demonstrate marked deterioration of the brain olfactory bulb in addition to brain targets that define the specific disease. In fact, the loss of the sense of smell may precede overt neurological symptoms by many years. This realization that the olfactory bulb is a common target in neurodegenerative diseases suggests the possibility that microbes and/or toxins in inhaled air may play a role in their pathogenesis. With regard to inhaled viruses, neuropathologists have focused on those viruses that infect and kill neurons. However, a recent study shows that a respiratory virus with no neurotropic properties can rapidly invade the mouse olfactory bulb from the nasal cavity. Available data suggest that this strain of influenza is passively transported to the bulb via the olfactory nerves (mechanism unknown), and is taken up by glial cells in the outer layers of the bulb. The infected glial cells appear to be activated by the virus, secrete proinflammatory cytokines, and block further spread of virus within the brain. At the time that influenza symptoms become apparent (15 h post-infection), but not prior to symptom onset (10 h post-infection), proinflammatory cytokine-expressing neurons are increased in olfactory cortical pathways and hypothalamus as well as in the olfactory bulb. The mice go on to die of pneumonitis with severe acute phase and respiratory disease symptoms but no classical neurological symptoms. While much remains to be learned about this intranasal influenza-brain invasion model, it suggests the hypothesis that common viruses encountered in our daily life may initiate neuroinflammation via olfactory neural networks. The numerous viruses that we inhale during a lifetime might cause the death of only a few neurons per infection, but this minor damage would accumulate over time and contribute to age-related brain shrinkage and/or neurodegenerative diseases. Elderly individuals with a strong innate inflammatory system, or ongoing systemic inflammation (or both), might be most susceptible to these outcomes. The evidence for the hypothesis that common respiratory viruses may contribute to neurodegenerative processes is developed in the accompanying article.

IFN-gamma triggers CCR2-independent monocyte entry into the brain during systemic infection by virulent Listeria monocytogenes

Listeria monocytogenes (Lm) is a bacterial pathogen that infects the brain via parasitized monocytes. CCR2 is important for monocyte migration into the brain after it is infected, but the degree of CCR2 involvement in monocyte migration to the CNS during systemic infection is less clear. Our recent data demonstrate that systemic infection with non-neuroinvasive DeltaactA Lm mutants triggers IFN-gamma-dependent brain influxes of Ly-6C(high) monocytes. Studies presented here tested the extent to which CCR2 and IFN-gamma are essential for monocyte migration to the brain during systemic infection with virulent Lm. For this, we assessed expression of monocyte-attracting chemokines in brains of normal and IFN-gamma mice during infection and tested the degree to which brain influxes of Ly-6C(high) monocytes were inhibited in chemokine- and chemokine receptor-deficient mice. In normal mice, systemic infection induced up-regulation of CCR2-binding (CCL2, CCL7, CCL8, CCL12) and CXCR3-binding chemokines (CXCL9, CXCL10). IFN-gamma mice had negligible mRNA and protein expression of CXCR3-binding chemokines, whereas expression of CCR2-binding chemokines was reduced, but remained significant. In addition, infection-triggered monocyte influxes were significantly reduced in IFN-gamma mice. Remarkably, brain monocyte influxes were normal during infection of CXCR3-, CCL2-, CCR1-, CCR5-, and CX3CR1-deficient mice. Influxes were transiently reduced in CCR2(-/-) mice, corresponding with retention of monocytes in the bone marrow but this was eventually overcome during infection. These data show that IFN-gamma is critical for triggering brain influxes of Ly-6C(high) monocytes during systemic infection with virulent Lm. This initial burst of monocyte migration is largely independent of individual chemokine receptors.

Recurrent systemic infections with Streptococcus pneumoniae do not aggravate the course of experimental neurodegenerative diseases

Neurological symptoms of patients suffering from neurodegenerative diseases such as Alzheimer's dementia (AD), Parkinson's disease (PD), or amyotrophic lateral sclerosis (ALS) often worsen during infections. We assessed the disease-modulating effects of recurrent systemic infections with the most frequent respiratory pathogen, Streptococcus pneumoniae, on the course of AD, PD, and ALS in mouse models of these neurodegenerative diseases [transgenic Tg2576 mice, (Thy1)-[A30P]alpha SYN mice, and Tg(SOD1-G93A) mice]. Mice were repeatedly challenged intraperitoneally with live S. pneumoniae type 3 and treated with ceftriaxone for 3 days. Infection caused an increase of interleukin-6 concentrations in brain homogenates. The clinical status of (Thy1)-[A30P]alpha SYN mice and Tg(SOD1-G93A) mice was monitored by repeated assessment with a clinical score. Motor performance was controlled by the tightrope test and the rotarod test. In Tg2576 mice, spatial memory and learning deficits were assessed in the Morris water maze. In none of the three mouse models onset or course of the disease as evaluated by the clinical tests was affected by the recurrent systemic infections performed. Levels of alpha-synuclein in brains of (Thy1)-[A30P]alpha SYN mice did not differ between infected animals and control animals. Plaque sizes and concentrations of A beta 1-40 and A beta 1-42 were not significantly different in brains of infected and uninfected Tg2576 mice. In conclusion, onset and course of disease in mouse models of three common neurodegenerative disorders were not influenced by repeated systemic infections with S. pneumoniae, indicating that the effect of moderately severe acute infections on the course of neurodegenerative diseases may be less pronounced than suspected.

Systemic inflammation induces acute working memory deficits in the primed brain: relevance for delirium

Delirium is an acute, severe neuropsychiatric syndrome, characterized by cognitive deficits, that is highly prevalent in aging and dementia and is frequently precipitated by peripheral infections. Delirium is poorly understood and the lack of biologically relevant animal models has limited basic research. Here we hypothesized that synaptic loss and accompanying microglial priming during chronic neurodegeneration in the ME7 mouse model of prion disease predisposes these animals to acute dysfunction in the region of prior pathology upon systemic inflammatory activation. Lipopolysaccharide (LPS; 100 μg/kg) induced acute and transient working memory deficits in ME7 animals on a novel T-maze task, but did not do so in normal animals. LPS-treated ME7 animals showed heightened and prolonged transcription of inflammatory mediators in the central nervous system (CNS), compared with LPS-treated normal animals, despite having equivalent levels of circulating cytokines. The demonstration that prior synaptic loss and microglial priming are predisposing factors for acute cognitive impairments induced by systemic inflammation suggests an important animal model with which to study aspects of delirium during dementia.

Regulation of learning and memory by meningeal immunity: a key role for IL-4

Proinflammatory cytokines have been shown to impair cognition; consequently, immune activity in the central nervous system was considered detrimental to cognitive function. Unexpectedly, however, T cells were recently shown to support learning and memory, though the underlying mechanism was unclear. We show that one of the steps in the cascade of T cell-based support of learning and memory takes place in the meningeal spaces. Performance of cognitive tasks led to accumulation of IL-4-producing T cells in the meninges. Depletion of T cells from meningeal spaces skewed meningeal myeloid cells toward a proinflammatory phenotype. T cell-derived IL-4 was critical, as IL-4(-/-) mice exhibited a skewed proinflammatory meningeal myeloid cell phenotype and cognitive deficits. Transplantation of IL-4(-/-) bone marrow into irradiated wild-type recipients also resulted in cognitive impairment and proinflammatory skew. Moreover, adoptive transfer of T cells from wild-type into IL-4(-/-) mice reversed cognitive impairment and attenuated the proinflammatory character of meningeal myeloid cells. Our results point to a critical role for T cell-derived IL-4 in the regulation of cognitive function through meningeal myeloid cell phenotype and brain-derived neurotrophic factor expression. These findings might lead to the development of new immune-based therapies for cognitive impairment associated with immune decline.

Leptin regulates leukocyte recruitment into the brain following systemic LPS-induced inflammation

The appetite suppressing hormone leptin has emerged as an important modulator of immune function and is now considered to be a critical link between energy balance and host defense responses to pathogens. These 'adaptive' responses can, in situations of severe and sustained systemic inflammation, lead to adverse effects including brain damage that is partly mediated by neutrophil recruitment into the brain. We examined the contribution of leptin to this process in leptin-deficient (ob/ob), -resistant (db/db) and wild-type (WT) mice injected intraperitoneally with a septic dose of lipopolysaccharide (LPS). This treatment induced a dramatic increase in the number of neutrophils entering the brain of WT mice, an effect that was almost totally abolished in the mutant mice and correlated with a significant reduction in the mRNA levels of interleukin-1beta, intracellular adhesion molecule-1 and neutrophil-specific chemokines. These effects were reversed with leptin replenishment in ob/ob mice leading to recovery of neutrophil recruitment into the brain. Moreover, 48 h food deprivation in WT mice, which decreased circulating leptin levels, attenuated the LPS-induced neutrophil recruitment as did a single injection of an anti-leptin antiserum 4 h before LPS treatment in WT mice. These results provide the first demonstration that leptin has a critical role in leukocyte recruitment to the brain following severe systemic inflammation with possible implications for individuals with altered leptin levels such as during obesity or starvation.

Mechanisms underlying inflammation in neurodegeneration

Inflammation is associated with many neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis. In this Review, we discuss inducers, sensors, transducers, and effectors of neuroinflammation that contribute to neuronal dysfunction and death. Although inducers of inflammation may be generated in a disease-specific manner, there is evidence for a remarkable convergence in the mechanisms responsible for the sensing, transduction, and amplification of inflammatory processes that result in the production of neurotoxic mediators. A major unanswered question is whether pharmacological inhibition of inflammation pathways will be able to safely reverse or slow the course of disease.

Microglia in neurodegenerative disease

Microglia, the resident macrophages of the CNS, are exquisitely sensitive to brain injury and disease, altering their morphology and phenotype to adopt a so-called activated state in response to pathophysiological brain insults. Morphologically activated microglia, like other tissue macrophages, exist as many different phenotypes, depending on the nature of the tissue injury. Microglial responsiveness to injury suggests that these cells have the potential to act as diagnostic markers of disease onset or progression, and could contribute to the outcome of neurodegenerative diseases. The persistence of activated microglia long after acute injury and in chronic disease suggests that these cells have an innate immune memory of tissue injury and degeneration. Microglial phenotype is also modified by systemic infection or inflammation. Evidence from some preclinical models shows that systemic manipulations can ameliorate disease progression, although data from other models indicates that systemic inflammation exacerbates disease progression. Systemic inflammation is associated with a decline in function in patients with chronic neurodegenerative disease, both acutely and in the long term. The fact that diseases with a chronic systemic inflammatory component are risk factors for Alzheimer disease implies that crosstalk occurs between systemic inflammation and microglia in the CNS.

Age-related changes in neural volume and microstructure associated with interleukin-6 are ameliorated by a calorie-restricted diet in old rhesus monkeys

Systemic levels of proinflammatory cytokines such as interleukin-6 (IL-6) increase in old age and may contribute to neural atrophy in humans. We investigated IL-6 associations with age in T1-weighted segments and microstructural diffusion indices using MRI in aged rhesus monkeys (Macaca mulatta). Further, we determined if long-term 30% calorie restriction (CR) reduced IL-6 and attenuated its association with lower tissue volume and density. Voxel-based morphometry (VBM) and diffusion-weighted voxelwise analyses were conducted. IL-6 was associated with less global gray and white matter (GM and WM), as well as smaller parietal and temporal GM volumes. Lower fractional anisotropy (FA) was associated with higher IL-6 levels along the corpus callosum and various cortical and subcortical tracts. Higher IL-6 concentrations across subjects were also associated with increased mean diffusivity (MD) throughout many brain regions, particularly in corpus callosum, cingulum, and parietal, frontal, and prefrontal areas. CR monkeys had significantly lower IL-6 and less associated atrophy. An IL-6xCR interaction across modalities also indicated that CR mitigated IL-6 related changes in several brain regions compared to controls. Peripheral IL-6 levels were correlated with atrophy in regions sensitive to aging, and this relationship was decreased by CR.

The role of exercise-induced myokines in muscle homeostasis and the defense against chronic diseases

Chronic inflammation is involved in the pathogenesis of insulin resistance, atherosclerosis, neurodegeneration, and tumour growth. Regular exercise offers protection against type 2 diabetes, cardiovascular diseases, colon cancer, breast cancer, and dementia. Evidence suggests that the protective effect of exercise may to some extent be ascribed to the antiinflammatory effect of regular exercise. Here we suggest that exercise may exert its anti-inflammatory effect via a reduction in visceral fat mass and/or by induction of an anti-inflammatory environment with each bout of exercise. According to our theory, such effects may in part be mediated via muscle-derived peptides, so-called "myokines". Contracting skeletal muscles release myokines with endocrine effects, mediating direct anti-inflammatory effects, and/or specific effects on visceral fat. Other myokines work locally within the muscle and exert their effects on signalling pathways involved in fat oxidation and glucose uptake. By mediating anti-inflammatory effects in the muscle itself, myokines may also counteract TNF-driven insulin resistance. In conclusion, exercise-induced myokines appear to be involved in mediating both systemic as well as local anti-inflammatory effects.

T cells facilitate recovery from Venezuelan equine encephalitis virus-induced encephalomyelitis in the absence of antibody

Venezuelan equine encephalitis virus (VEEV) is a mosquito-borne RNA virus of the genus Alphavirus that is responsible for a significant disease burden in Central and South America through sporadic outbreaks into human and equid populations. For humans, 2 to 4% of cases are associated with encephalitis, and there is an overall case mortality rate of approximately 1%. In mice, replication of the virus within neurons of the central nervous system (CNS) leads to paralyzing, invariably lethal encephalomyelitis. However, mice infected with certain attenuated mutants of the virus are able to control the infection within the CNS and recover. To better define what role T cell responses might be playing in this process, we infected B cell-deficient microMT mice with a VEEV mutant that induces mild, sublethal illness in immune competent mice. Infected microMT mice rapidly developed the clinical signs of severe paralyzing encephalomyelitis but were eventually able to control the infection and recover fully from clinical illness. Recovery in this system was T cell dependent and associated with a dramatic reduction in viral titers within the CNS, followed by viral persistence in the brain. Further comparison of the relative roles of T cell subpopulations within this system revealed that CD4(+) T cells were better producers of gamma interferon (IFN-gamma) than CD8(+) T cells and were more effective at controlling VEEV within the CNS. Overall, these results suggest that T cells, especially CD4(+) T cells, can successfully control VEEV infection within the CNS and facilitate recovery from a severe viral encephalomyelitis.

Association of C-reactive protein with cognitive impairment

BACKGROUND

High-sensitivity C-reactive protein (hsCRP) is a biomarker of cardiovascular risk that is suggested to be a biomarker for cognitive impairment.

OBJECTIVE

To explore the association between hsCRP and cognitive impairment.

DESIGN

Cross-sectional analysis of a population-based community aging study.

SETTING

Northern Manhattan, New York, New York.

OTHER PARTICIPANTS

One thousand three hundred thirty-one participants from a longitudinal study of aging without dementia and with available hsCRP and neuropsychological testing data at baseline.

MAIN OUTCOME MEASURES

Four cognitive scores (memory, visuospatial, executive, and language impairment) derived from a neuropsychological battery. Cognitive impairment was defined by scores below 1.5 SDs of demographically corrected means.

RESULTS

Participants in the highest hsCRP tertile had higher adjusted odds of impaired memory (odds ratio [OR], 1.5; 95% confidence interval [CI], 1.0-2.1; P = .03) than participants in the lowest tertile. Subjects in the highest hsCRP tertile also had greater odds of visuospatial impairment (OR, 1.6; 95% CI, 1.0-2.3; P = .03). Higher hsCRP was not associated with executive or language impairment. Persons with at least 1 APOE epsilon4 allele and hsCRP in the highest tertile had the greatest odds of impaired memory (OR, 2.7; 95% CI, 1.6-4.4).

CONCLUSIONS

High hsCRP may be a marker of memory and visuospatial impairment in the elderly. The role of APOE epsilon4 requires further exploration.

Inflammation in Alzheimer's disease: relevance to pathogenesis and therapy

Evidence for the involvement of inflammatory processes in the pathogenesis of Alzheimer's disease (AD) has been documented for a long time. However, the inflammation hypothesis in relation to AD pathology has emerged relatively recently. Even in this hypothesis, the inflammatory reaction is still considered to be a downstream effect of the accumulated proteins (amyloid beta (Abeta) and tau). This review aims to highlight the importance of the immune processes involved in AD pathogenesis based on the outcomes of the two major inflammation-relevant treatment strategies against AD developed and tested to date in animal studies and human clinical trials - the use of anti-inflammatory drugs and immunisation against Abeta.